I just witnessed the big switch a roo at the end of a Nordic event. Winner was kneeling on the ground next to his skis giving thanks and catching his breath.. In front of him were three identical pairs of podium skis that were the same brand as his own but not the same.. Someone walked up and snatched away the skis he had just stepped out of to collapse in a heap and recover.
There's few reason for this. First, race skis are full of markings (you are allowed to change only one ski during race, so skis are marked before start, and markings are checked in finish, so slowly your skis get worse then school book of super bored student
, and that certainly doesn't look good on tv. Next reason is, that in xc skis are way more important then in alpine. In alpine you can still win with basically wooden plank under the feet, while in xc you can't do anything with bad skis. Now if you will be dragging your good and fast skis (especially without transport wax on ptex) around during medal ceremony, interview, autograph signing and taking photos with kids, sooner or later something bad will happen to skis. And then there's third reason, once you finish race, there can be snow on skis, on classic races there's stick wax on bottom etc. Company's tech in finish area has new pair of perfectly clean, neatly tied together ski which he gives to racer, so everything looks nice on tv and photos. But contrary to alpine, skis in xc (including biathlon and nordic combined) are real race skis. They are not skis good enough to win WC on them, but they are race model, as in xc companies try to sell real race skis and not lower end models. There's difference between alpine and xc, as in alpine you will actually ski worse with real race ski then with lower end ski, unless you (your power and ski technique) are able to drive it, while in xc, you won't ski better with real race ski, but you also won't ski worse.. and you pay twice as much for race model then for lower end model, so all is good for ski company